Molecular Systems for Nonlinear Optical Applications

Abstract

Organic nonlinear optical materials have developed to the point where applications in practical devices may now be contemplated. For second order nonlinear systems, these applications fall into two classes: frequency doubling and electro-optic switching and modulation. Chromophores already exist with values of the second order molecular hyperpolarizability β large enough for electro-optic applications. The situation for frequency doubling is not nearly as promising. The absorption maximum of the chromophore and the magnitude of β cannot be independently optimized within a given class of chromophores (e.g. benzenes, stilbenes, tolanes). Large values of β seem to be correlated with absorption maxima that are shifted to long wavelengths. This means that those chromophores that are the most efficient for frequency doubling will also be the most likely to absorb photons generated at the second harmonic wavelength. This relationship can be easily understood, at least in principle, by referring to a simple Hückel model of a prototypical nonlinear chromophore. © 1992, Taylor & Francis Group, LLC. All rights reserved.